A tape cartridge having a leader block provided therein has been used for a magnetic instrument which is provided as a peripheral equipment for a computer to back up informations. The leader block is connected to a leader end of a tape wound on a single reel in the tape cartridge to guide the tape along a predetermined guide path to a winding reel in the magnetic instrument while it is associated with a drawing pin member in the magnetic instrument.
Such a drawing pin member is disclosed in Japanese Application Publication No. 13,097/1984, for example. In the prior art, there is provided a cylindrical drawing pin member including a thinner cylindrical portion and an enlarged end provided integrally with the end of the cylindrical portion to engage a slot in the leader block which slot has a recess provided corresponding to the enlarged end. In operation, the cylindrical portion is inserted into the slot with the enlarged end being shifted from the slot and then the tape cartridge is moved whereby the leader block is moved in a direction in which the drawing pin member extends to engage the recess with the enlarged end so that the leader block is connected to the drawing pin member. Such a movement of the drawing pin member is accomplished by a linkage.
The peripheral equipment for the computer has been compacted, which requires the magnetic instrument to be also compacted. However, since the drawing pin member has at least a length which is equal to the total of the slot length of the leader block and the movement length thereof, the length of the drawing pin member becomes larger, which causes the magnetic instrument to be higher and the strength of the drawing pin member to be poorer. This prevents the drawing pin member from being accurately positioned.